The present invention is a zeolite composition. In particular, it is a rare-earth exchanged form of zeolite Q.
Zeolite Q is a well-known zeolite (U.S. Pat. No. 2,991,151), having no useful properties because it shows major structural collapse on dehydration at temperatures as low as 240.degree. C. This is almost unique amongst silica-alumina zeolites, most of which are stable to dehydration. Because of its low chemical and thermal stability, no structural work on Q has successfully definitively defined its framework topology. A review by Sherman (A.C.S. Symp. Ser. 40, p. 30 (1977)) equated zeolite Q with zeolite KI, and the Q-KI composition may be defined as: EQU KAlSiO.sub.4.xH.sub.2 O
The Si/Al ratio is always unity, and the hexagonal unit cell is a=13.multidot.4.ANG., c=13.multidot.2 .ANG.. A recent study by Andries et al (Zeolites, v. 11, p. 116; 124 (1991)) shows that this zeolite probably has a 12-ring channel perpendicular to the platelet crystals--an analogous structure to the BePO.sub.4 -H material (Harvey, Zeit. Kristallogr., v. 182, p. 123 (1988)). Q should therefore have useful catalytic and sorption properties, if it can be stabilized.
The original patent gives properties for a variety of cation exchanged forms of Q (Na, Li, K, Ca, Mg, Zn, Sr, Ba), indicating that they have properties characteristic of a small pore molecule sieve, and the pore size is given by Sherman as 3.6 .ANG., characteristic of 8-rings. The major deficiency of Q is that its structure collapses at about a temperature of 230.degree. C.--an exceedingly low temperature for a zeolite, and possibly indicative of a highly hydroxylated structure ---and that it has low stability at pH below about 6.5.